Lets step just slightly aside and see if a related question leads to new insight… a bit of lateral thinking as it were.
Science fiction proposes that we might someday manage to clone brain tissue and enclose that tissue in a mechanical housing. This is typically refered to as a “cyborg.” Could this human brain have a soul?
Take yet another step and ask “If science manages to clone a human being, would that cloned human have a soul?” The difference between a clone and an “in vitro” fertilization is pretty small, so if we say, “no, a clone has no soul” then we are saying that the soul is created (by God) at the moment the sperm meets the egg. This is certainly theologically sound, but it implies the very frightening possibility that a man could be equal to me - to us - in every respect of intelligence, self-awareness, emotional responses of love, hate, disappointment and heartbreak, and yet be without a soul. Wow. I think the only possible answer to this question is “Only God knows, so we must assume this created being does have a soul” and give the clone all the rights of any other person, including the right to be a priest or whatever he wants.
So once you grant the clone that status, you are required to grant the cyborg the same status. It is still a human brain, functionally identical to our brains, just in a different body… almost as if a person gradually had his heart and lungs and limbs replaced by artificial mechanical devices. So from A to B, we have cyborgs that have souls.
Finally take the step back to a non-organic brain. One that runs in silicon or something new, but that is not a test tube grown brain. Lets imagine that this artificial brain is not fully pre-programmed. It is given some basic level of functionality - enough language to get it started. Just as with a child, it is a learning being. It learns to call things by their right names, and gradually learns to operate in the context of the physical and the social environment. Each one of these creatures would be different because no matter how hard you worked to give them identical upbringing, there would be variations in the conversations they would have, in the way different people react to them, in what they see and hear and learn. As with people, their experiences and memories would guide their behavior. As with people, their “programming” would be largely self-developed, guided by infinite variations of environment and choice.
I am just conjecturing here of course… thinking of Asimov’s positronic robots that are possessed of free-will, desires, hopes, and fears…
Once a thinking being exhibits every sign of humanity… intelligence, emotion, free-will, etc… it seems that from a practical sense, our only option is to assume it has a soul and accord it all the rights of any human being. The right to pray. The right to baptism, the sacrament, and confession? The right to become a priest? We would have absolutely no evidence or grounds for denying this creature those rights and would be compelled to leave that up to God.